Guide for Sound Insulation in Wood Frame Construction Part 3 ppt

Page 22 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Summary – Vertical Flanking in Typical Constructions For the case of two apartments vertically separated by a floor/ceiling assembly, the Apparent-STC between the two occupancies is systematically less than the STC for direct transmission through the separating floor. There are three main issues: 1. The main flanking path is consistently from the subfloor of the room above to the walls of the room below or vice versa, if the subfloor is a layer of oriented strand board (OSB) or of plywood directly fastened to the top of the floor joists. 2. Some changes in the wall below can significantly reduce transmission via a specific wall surface. Adding a second layer of gypsum board reduces flanking. Mounting gypsum board on resilient channels should reduce flanking to insignificance for most practical floor assemblies. 3. Reduction of Apparent-STC by flanking depends on the flanking transmission via all walls of the room below. Airborne Sound Source Direct Transmission through floor Airborne Sound Source Airborne Sound Source Direct Transmission through floor Airborne Sound Source Direct Transmission through floor Airborne Sound Source As discussed in the detailed report [1], the estimates in this section should be applied only for cases where wall and floor details are within the range of the tested specimens (links to specifications are in section on Changes to Control Horizontal Flanking) This Guide ignores the vertical sound transmission between stories within a single occupancy where the gypsum board ceiling is screwed directly to the floor joists (called “row housing” in later sections) Page 23 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Changes to Control Vertical Flanking between Apartments (One apartment above another, Airborne Sound Source) For the case of two apartments vertically separated by a floor/ceiling assembly (vertical transmission): 1. Changes to control flanking must be focused on the elements of the dominant flanking path. 2. The two surfaces that can be modified to reduce flanking transmission are the walls in the room below, and the floor surface in the room above. 3. Effects of some common changes are presented in this section Airborne Sound Source Direct Transmission through floor Airborne Sound Source Airborne Sound Source Direct Transmission through floor Airborne Sound Source Direct Transmission through floor Airborne Sound Source The effects of simple changes to the walls of the room below are presented in detail in the earlier section on flanking in typical basic constructions. The combined flanking transmission via all walls of the room below must be considered. Typical Apparent-STC values are listed in the Table of Typical Vertical Flanking • The worst case is with a single layer of gypsum board directly attached to the studs of all the walls below. • Adding a second layer of directly attached gypsum board provides slight reduction in the flanking transmission. • If the gypsum board is mounted on resilient metal channels, the flanking via that surface is reduced enough so that it can be ignored. Any such walls need not be included as significant when assessing flanking transmission. Note that resilient channels must be mounted between the studs and the gypsum board, not between two layers of gypsum board. In addition to the effect of specific gypsum board treatment of the walls in the room below, the Apparent-STC can also be improved by changing the floor surface. • Adding a topping over a basic plywood or OSB subfloor gives more attenuation both for direct transmission through the floor and for the dominant flanking transmission paths. • The change in flanking due to adding a topping depends on the type of topping and on the orientation of the floor joists relative to the flanking wall. However, an average value can be used as a slightly conservative design estimate because the floor joists are normally parallel to some walls in the room below and perpendicular to others. Page 24 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Table of Change in Vertical Flanking due to Toppings The following Table shows the change in Apparent-STC expected from adding a topping, including both direct transmission through the floor/ceiling and flanking transmission via the walls of the room below. Worse Ceiling 1 layer of gypsum board on resilient metal channels @400mm (Direct STC 51 with no topping) Basic Ceiling 2 layers of gypsum board on resilient metal channels @400mm (Direct STC 55 with no topping) Better Ceiling 2 layers of gypsum board on resilient metal channels @600 mm (Direct STC 59 with no topping) Walls in room below Floor Topping For case with no floor topping, get Apparent-STC from the Table of Typical Vertical Flanking For the complete system including a topping, add (to the Apparent-STC without a topping) a value chosen from table below Stapled 19 mm OSB topping +5 +6 +7 Bonded 25 mm gypsum concrete topping +10 +9 +9 All Walls with 1 or 2 layers of gypsum board applied directly to the studs in room below 38 mm gypsum concrete topping on resilient mat +14 +13 +12 Stapled 19 mm OSB topping +4 +5 +5 Bonded 25 mm gypsum concrete topping +11 +11 +11 All Walls with resilient channels supporting gypsum board in room below (No flanking) 38 mm gypsum concrete topping on resilient mat +15 +15 +15 Note1: Specifications and detail drawings for the basic assemblies and added toppings are given in the following section on Changes to Control Horizontal Flanking. Values in this table were obtained from evaluation of a limited set of specimens built with specific products that are identified in the detailed descriptions. Using “generic equivalents” may change results. Note2: Results will be about the same for one or two layers of resiliently mounting the gypsum board because in either case flanking paths do not contribute significantly relative to the direct path. Page 25 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Horizontal Flanking in Wood-framed Constructions One apartment beside the other, airborne sound source) For the case of two apartments horizontally separated by a partition wall assembly, there are two key issues: Transmission via floor surfaces (Ceiling surfaces isolated) Transmission through wall Airborne Sound Source Transmission via floor surfaces (Ceiling surfaces isolated) Transmission through wall Airborne Sound Source 1. The main flanking path is consistently from the floor of one room to the floor of the room beside, if the subfloor is a continuous layer of oriented strand board (OSB) or of plywood directly fastened to the top of the floor joists. 2. Reduction of Apparent-STC may be affected by details of the floor assembly, the wall assembly, and the continuity of structural elements across the floor/wall junction. Note that the above assumes that other horizontal paths (wall-wall and ceiling-ceiling paths) are not significant. This will be the case if there are resilient channels or other vibration breaks in such paths. Several “row housing” cases, where the ceiling is not on resilient channels, are presented in a later section; with a basic subfloor, they exhibit very similar horizontal flanking to the cases in this section. To highlight the key factors influencing horizontal flanking across floor/wall junctions, a number of typical configurations are presented, proceeding from cases where the flanking effect is rather small to cases where flanking drastically reduces the sound isolation. Page 26 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 With the subfloor continuous across the junction at a double stud wall, Apparent- STC is appreciably below the STC 55 for direct transmission through the separating wall. Link to Corresponding Impact Apparent STC 50 to 51 Flanking via subfloor Direct Transmission STC 55 Floor joists perpendicular to separating wall (loadbearing wall) Apparent STC 50 to 51 Flanking via subfloor Direct Transmission STC 55STC 55 Floor joists perpendicular to separating wall (loadbearing wall) The Apparent-STC may be changed by specific changes in the floor assembly, or the wall assembly, or the fire block at floor/wall junction. Change in Construction Typical Effect Apparent STC Changing Floor 16 mm OSB subfloor ⇒ plywood subfloor not significant 50 — 51 Changing Wall Double gypsum board on each side and insulation on each side (Direct STC 66) Improvement depends on fire block 52 — 66 depends on fire block Changing Floor/Wall Junction Subfloor break at wall cavity Improvement depends on fire block 50 — 50 depends on fire block Some of the changes listed in the table are inter-dependent. As well, flanking via sidewalls (such as an exterior wall or corridor wall perpendicular to the separating wall shown) can cause further reduction of the Apparent-STC. The effects of these combined flanking paths are presented on the following page, for some typical generic fire blocks. Page 27 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Fire blocks are required to stop the spread of fire through concealed cavities such as that between the two rows of studs in the wall illustrated above. The performance of such systems is discussed in an IRC/NRC publication [ 3]. As noted in that publication, as well as performing their intended function of controlling fire, these treatments at the floor/wall junction can significantly worsen flanking transmission. The effect of fire blocks depends on the associated constructions. Two separating walls are considered – basic (as shown above in the figure) that provides Direct-STC 55, and a better wall (with double gypsum board on each side, and cavity insulation on each side) that provides Direct-STC 66. The table also presents two alternatives for the sidewall – with the gypsum board either directly screwed to the studs and continuous across the partition wall or mounted on resilient channels and discontinuous across the partition wall. For each of these construction cases, the table presents the Apparent –STC for four variants of fire block at the floor/wall junction. Separating wall Basic Wall (STC 55) Better Wall (STC 66) Sidewall gypsum board Direct or resilient Direct Resilient Fire Block Alternatives (Apparent-STC) Continuous OSB or Plywood 49 51 52 0.38 mm sheet steel 50 54 57 Coreboard (between joist headers) 50 54 57 Fibrous material (glass fibre or rock fibre of suitable density) 50 54 66 No material in gap N/A N/A 66 The performance of fire blocks (for both sound and fire) is addressed further in References 3 and 4. The tabulated values show that to attain Apparent-STC 55 or better with the basic OSB subfloor, it may be necessary to select an appropriate fire block and an improved separating wall and adequately treat flanking paths involving the sidewalls. In practice, a fire block formed by continuous OSB or plywood subfloor may be required to provide structural support, especially in regions where strong lateral loading from winds or seismic activity is expected.  For row housing this may be a lesser concern. The fibrous fire blocks that cause negligible flanking transmission across the cavity of the separating double stud wall offer an effective solution in those cases.  Continuous OSB or plywood subfloor is the typical solution for multi- storey apartment construction. In such cases, the use of a topping may be required, and this is addressed in later sections. Page 28 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 With the subfloor continuous across the junction at a double stud wall, and floor joists parallel to the wall, the Apparent-STC is even farther below the STC 55 for direct transmission through the separating wall. Link to Corresponding Impact Apparent STC 46 to 47 STC 55 Direct Transmission Flanking via subfloor Floor joists parallel to separating wall (non-loadbearing wall) Apparent STC 46 to 47 STC 55 Direct Transmission Flanking via subfloor Floor joists parallel to separating wall (non-loadbearing wall) The Apparent-STC may be changed by specific changes in the floor assembly, or the wall assembly, or the fire block at floor/wall junction. Change in Construction Typical Effect Apparent STC Changing Floor 16 mm OSB subfloor ⇒ plywood subfloor dimensional wood floor joists ⇒ wood-I joists not significant 46 — 47 Changing Wall Double gypsum board on each side and insulation on each side (Direct STC 66) Improvement depends on fire block 45 — 62 depends on fire block Changing Floor/Wall Junction Subfloor break at wall cavity Improvement depends on fire block 45 — 49 depends on fire block Some of the changes listed in the table are inter-dependent. As well, flanking via sidewalls (such as an exterior wall or corridor wall perpendicular to the separating wall shown) can cause further reduction of the Apparent-STC. Page 29 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 The effect of fire blocks depends on the associated constructions. Two separating walls are considered – basic (as shown above in the figure) that provides Direct-STC 55, and a better wall (with double gypsum board on each side, and cavity insulation on each side) that provides Direct-STC 66. The table also presents two alternatives for the sidewall – with the gypsum board either directly screwed to the studs and continuous across the separating wall or mounted on resilient channels and discontinuous across the separating wall. For each of these construction cases, the table presents the Apparent-STC for four variants of fire block at the floor/wall junction. Separating wall Basic Wall (STC 55) Better Wall (STC 66) Sidewall gypsum board Direct or resilient Direct Resilient Fire Block Alternatives (Apparent–STC) Continuous OSB or Plywood 45 47 48 None, or fibrous material 54 62 The tabulated values show that it is not possible to attain Apparent-STC 50 or better with the continuous basic OSB subfloor, regardless of the separating wall, or the mounting and continuity of the sidewall gypsum board. Not all of the fire blocking materials were examined when the joists are parallel to the wall/floor junction. However, comparing the case of the continuous OSB of this case (parallel) to the previous (perpendicular) suggests that the Apparent- STC will be lower when the joists are parallel to the junction. As with the case where the joists are perpendicular to the wall/floor junction (previous case), attaining an Apparent-STC of 55 or better can only be done through attention to an appropriate fire block and an improved separating wall and adequate treatment of flanking paths involving the sidewalls. In practice, a fire block formed by continuous OSB or plywood subfloor may be required to provide structural support, especially in regions where strong lateral loading from winds or seismic activity is expected.  For row housing this may be a lesser concern. The fibrous fire blocks that cause negligible flanking transmission across the cavity of the separating double stud wall offer an effective solution in those cases.  Continuous OSB or plywood subfloor is the typical solution for multi- storey apartment construction. In such cases, the use of a topping may be required, and this is addressed in later sections. Page 30 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 With the floor joists parallel to the separating wall, changing from the double stud wall to a simpler single stud wall assembly permits more transfer of structural vibration across the junction, and hence lowers the Apparent-STC to about 45. Link to Corresponding Impact STC 52 Apparent STC 42 to 45 Alternate junction details Direct Transmission Flanking via subfloor Floor joists parallel to separating wall (non-loadbearing wall) STC 52 Apparent STC 42 to 45 Alternate junction details Direct Transmission Flanking via subfloor Floor joists parallel to separating wall (non-loadbearing wall) Changing the wall assembly has only slight effect on the Apparent-STC, except that the shear wall lowers the Apparent-STC to 42. Separating wall Basic Wall (STC 52) Better Wall (STC 57) Change in Construction Effect (Apparent–STC) Changing Floor/Wall Junction Subfloor break at wall or alternate fire block details slightly worse (shear wall is worst) 42 — 45 43 — 46 Sidewall Gypsum Board Directly attached ⇒ Resiliently mounted not significant* 44 46 Note * Directly attaching the gypsum board of the sidewall is not significant when the subfloor is continuous and bare, as shown here. When a topping is applied, however, sidewall paths become important and can limit the Apparent-STC to 54, as shown later. Page 31 of 103 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 With the single stud wall assembly, changing orientation of the floor joists from parallel to the separating wall to perpendicular gives more transfer of structural vibration across the floor and alters the junction; this lowers the Apparent-STC even further, to about 43. Link to Corresponding Impact STC 52 Direct Transmission Apparent STC 43 Flanking via subfloor & joists Floor joists perpendicular to separating wall (loadbearing wall) In this case, the transmission from floor to floor is clearly dominant, so improving the separating wall to Direct STC 57 does not affect the overall Apparent-STC (and greater improvements in the wall would have the same minimal benefit.) Separating wall Basic Wall (STC 52) Better Wall (STC 57) Change in Construction Effect (Apparent–STC) Changing Floor/Wall Junction Subfloor break at wall not significant 43 43 Sidewall Gypsum Board Directly attached ⇒ Resiliently mounted not significant* 43 43 Note * Directly attaching the gypsum board of the sidewall is not significant when the subfloor is continuous and bare, as shown here. When a topping is applied, however, sidewall paths become important and can limit the Apparent-STC to 54, as shown later. [...]... attached ⇒ Resiliently mounted not significant* 37 37 Note * Directly attaching the gypsum board of the sidewall is not significant when the subfloor is continuous and bare, as shown here When a topping is applied, however, sidewall paths become important and can limit the Apparent-STC to 54, as shown later IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 ... separating wall (loadbearing wall) In this case, the transmission from floor to floor is so dominant that improving the separating wall to a Direct STC of 57 has negligible effect on the overall Apparent-STC Basic Wall (STC 52) Separating wall Change in Construction Effect Better Wall (STC 57) (Apparent–STC) Changing Floor/Wall Junction Subfloor break at wall not significant 37 37 Sidewall Gypsum Board... 32 of 1 03 With the subfloor and the joists continuous across the floor/wall junction, but the same single stud wall assembly and floor details, there is more transfer of structural vibration across the junction This lowers Apparent-STC below 40 Link to Corresponding Impact STC 52 Direct Transmission Flanking via subfloor & joists Apparent STC 37 Floor joists continuous and perpendicular to separating . Page 22 of 1 03 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Summary – Vertical Flanking in Typical Constructions For the case of two apartments vertically. housing” in later sections) Page 23 of 1 03 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 Changes to Control Vertical Flanking between Apartments (One apartment. addressed in later sections. Page 30 of 1 03 IRC RR-219: Guide for Sound Insulation in Wood Frame Construction March 2006 With the floor joists parallel to the separating wall, changing from